Semiconductor device and power converter including a copper film with a small grain size stress relaxtion layer
A semiconductor device that includes a semiconductor layer disposed on a semiconductor substrate, a first semiconductor region provided in an upper layer portion of the semiconductor layer, a second semiconductor region provided in an upper layer portion of the first semiconductor region, a gate insulation film, a gate electrode, a first main electrode that is provided on an interlayer insulation film that covers the gate electrode and that is electrically connected to the second semiconductor region via a contact hole, and a second main electrode disposed on a second main surface of the semiconductor substrate. The first main electrode includes an underlying electrode film connected to the second semiconductor region via the contact hole, and a copper film provided on the underlying electrode film. The copper film includes at least a portion that serves as a stress relaxation layer having a smaller grain size than the other portion of the copper film.
1. A semiconductor device comprising:
a semiconductor substrate;
a semiconductor layer of a first conductivity type disposed on a first main surface of the semiconductor substrate;
a first semiconductor region of a second conductivity type selectively provided in an upper layer portion of the semiconductor layer;
a second semiconductor region of the first conductivity type selectively provided in an upper layer portion of the first semiconductor region;
a gate insulation film provided in contact with surfaces of the first and second semiconductor regions and the semiconductor layer;
an insulation film that is thicker than the gate insulation film and provided in a region of the semiconductor layer in which the gate insulation film is not provided;
a gate electrode provided on at least the gate insulation film;
an interlayer insulation film provided to cover the gate electrode;
a contact hole formed through the gate insulation film and the interlayer insulation film and exposing at least the second semiconductor region at a bottom thereof;
a first main electrode provided on the interlayer insulation film and electrically connected to the second semiconductor region via the contact hole; and
a second main electrode disposed on a second main surface of the semiconductor substrate,
wherein the first main electrode includes:
an underlying electrode film connected to the second semiconductor region via the contact hole; and
a copper film provided on the underlying electrode film, and
the copper film has a thickness greater than or equal to 15 μm, and
the copper film includes a stress relaxation layer which is outside of said contact hole and has a smaller grain size than another portion of the copper film, the stress relaxation layer being above a region that includes at least a junction between the gate insulation film and the insulation film.
2. The semiconductor device according to claim 1 , further comprising:
an external connection line electrically connected to the copper film; and
the sealing resin provided on the copper film that includes the external connection line,
wherein the stress relaxation layer is provided at a junction between the sealing resin and the copper film.
3. The semiconductor device according to claim 1 , wherein
the grain size of the stress relaxation layer is in a range of 0.1 to 1 μm.
4. The semiconductor device according to claim 1 , wherein
the underlying electrode film includes asperities on at least a part of a surface in contact with the copper film.
5. The semiconductor device according to claim 1 , wherein
the semiconductor substrate is a silicon carbide semiconductor substrate.
6. A power converter comprising:
a main converter circuit that includes the semiconductor device according to claim 1 and converts and outputs input power;
a drive circuit that outputs a driving signal for driving the semiconductor device to the semiconductor device; and
a control circuit that outputs a control signal for controlling the drive circuit to the drive circuit.